GTL2008PW,112

GTL2008PW,112 2. Features and benefits

(cid:132) Operates as a GTL to LVTTL sampling receiver or LVTTL to GTL driver(cid:132) Operates at GTL−/GTL/GTL+ signal levels(cid:132) EN1 and EN2 disable error output(cid:132) All LVTTL and GTL outputs are put in a high-impedance state when EN1 and EN2 areLOW(cid:132) 3.0 V to 3.6 V operation(cid:132) LVTTL I/O not 5 V tolerant(cid:132) Series termination on the LVTTL outputs of 30 Ω(cid:132) ESD protection exceeds 2000 V HBM per JESD22-A114, 150 V MM perJESD22-A115, and 1000 V CDM per JESD22-C101

GTL2008PW,112 1. General description

The GTL2008 is a customized translator between dual Xeon processors, Platform HealthManagement, South Bridge and Power Supply LVTTL and GTL signals.Functionally and footprint identical to the GTL2007, the GTL2008 LVTTL and GTL outputswere changed to put them into a high-impedance state when EN1 and EN2 are LOW, withthe exception of 11BO because its normal state is LOW, so it is forced LOW. EN1 andEN2 will remain LOW until VCC is at normal voltage, the other inputs are in valid statesand VREF is at its proper voltage to assure that the outputs will remain high-impedancethrough power-up.The GTL2008 has the enable function that disables the error output to the monitoringagent for platforms that monitor the individual error conditions from each processor. Thisenable function can be used so that false error conditions are not passed to themonitoring agent when the system is unexpectedly powered down. This unexpectedpower-down could be from a power supply overload, a CPU thermal trip, or some otherevent of which the monitoring agent is unaware.A typical implementation would be to connect each enable line to the system power goodsignal or the individual enables to the VRD power good for each processor.Typically Xeon processors specify a VTT of 1.1 V to 1.2 V, as well as a nominal Vref of0.73 V to 0.76 V. To allow for future voltage level changes that may extend Vref to 0.63 ofVTT (minimum of 0.693 V with VTT of 1.1 V) the GTL2008 allows a minimum Vref of 0.66 V.Characterization results show that there is little DC or AC performance variation betweenthese Vref levels.